[Bug rtl-optimization/39338] reduction of in-loop 64-bit multiply to repeated add wrong when loop var wraps neg

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2009-03-02 10:03 -------
 int i = 0;
 for (i = 1; i; ++i) {

invokes undefined behavior (signed overflow is undefined in ISO C).

Use -fwrapv or unsigned arithmetic.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39338